Distillation of diacetylenically unsaturated aromatic hydrocarbons

ABSTRACT

A process for the distillation of high boiling diacetylenically unsaturated compounds comprising subjecting said high boiling diacetylenically unsaturated compounds to distillation conditions within a distillation zone in the presence of a higher boiling inert hydrocarbon diluent, said diluent having a minimum boiling point at least 5*C higher than the boiling point of said diacetylenically unsaturated compound being distilled, the distillation being carried out under vacuum sufficient to maintain a maximum distillation temperature below 150*C.

United States Patent [1 1 1 3,850,757 Looney 1 Nov. 26, 1974 [54] DISTILLATION F DIACETYLENICALLY 3,117,167 1/1 964 Burch et a1. 260/6665 A 3,360,443 12/1967 Apotheker 203/9 g g g g 2 TIC 3,408,265 10/1968 Ward 203/9 3,419,476 12/1968 Hagedorn 203/52 [76] Inventor: Jesse M. Looney, 611 Colgate, Big 3,436,318 4/1969 Glass 203/9 Spring, 79720 3,594,437 7 1971 White 260/674 R [22] Flled: June 1973 Primary Examiner-Wilbur L. Bascomb, Jr. [21] Appl. No.: 373,179

Related US. Application Data [57] ABSTRACT [63] Continuation-impart of Ser. No. 105,726, Jan. 11, A process for the distillation of high boiling lgnabandoned diacetylenically unsaturated compounds comprising subjecting said high boiling diacetylenically unsatu- [52] Cl g g rated compounds to distillation conditions within a 51 I t Cl Bold 3/34 (307/ 7/00 distillation zone in the presence of a higher boiling 668 R R 2 5 inert hydrocarbon diluent, said diluent having a minil 0 earc 6 8 52 70 mum boiling point at least 5C higher than the boiling point of said diacetylenically unsaturated compound 9 b d References Cited being lstilled the lsti lation emg carried out un er UNITED STATES PATENTS Coulter 203/9 vacuum sufficient to maintain a maximum distillation temperature below C.

3 Claims, N0 Drawings DISTILLATION OF DIACETYLENICALLY UNSATURATED AROMATIC HYDROCARBONS CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of copend ing application Ser. No. 105,726, filed Jan. 11, 1971 and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the distillation of readily polymerizable unsaturated hydrocarbons. More particularly, the present invention relates to a process for the distillation of the readily polymerizable high boiling diacetylenically unsaturated aromatic hydrocarbons, i.e., diethynylbenzene, methyl diethynylbenzenes, whereby polymer formation is substantially reduced.

The diacetylenically unsaturated hydrocarbons such as diethynylbenzene, readily polymerize when subjected to elevated temperatures. These compounds are high boiling, i.e., diethynylbenzene boiling point approximately 190C at atmospheric pressure, and even when high vacuum is used in their distillation, signif1- cantly elevated temperatures are still required in order to get a boil-up of the diacetylenically unsaturated compounds. Such elevated temperatures result in significant polymer formation with the attendant loss of desired product and the fouling and plugging of the distillation apparatus. The use of the well-known and widely used conventional polymerization inhibitors such as tert-butyl catechol, sulfur, hydroquinone, and the like, which work relatively effectively for most vinyl compounds, does not significantly, if at all, reduce polymer formation even in the high vacuum distillation of the diacetylenically unsaturated aromatic hydrocarbons.

It is an object of the present invention to provide a new and improved process for the distillation of high boiling diacetylenically unsaturated hydrocarbons.

Anotherobject of the presentinventionis to provide a new and improved process for the distillation of high boiling diacetylenically unsaturated hydrocarbons whereby such hydrocarbons may be readily distilled with substantially reduced polymer formation.

Additional objects will become apparent from the following description of the invention herein disclosed.

SUMMARY OF THE INVENTION The present invention, which fulfills these and other objects, is a process for the distillation of high boiling diacetylenically unsaturated compounds comprising subjecting said high boiling diacetylenically unsaturated compounds to distillation conditions within a distillation zone in the presence of a higher boiling inert hydrocarbon diluent, said diluent having a minimum boiling point at least 5C higher than the boiling point of said diacetylenically unsaturated compound being distilled.

By means of the distillation process of the present invention, diacetylenically unsaturated compounds such as diethynylbenzene may be distilled at relatively high temperatures with substantially reduced polymer formation as compared to that normally obtained under high vacuum distillation conditions alone and/or in the presence of conventional polymerization inhibitors.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION The distillation process of the present invention is carried out in the presence of an inert hydrocarbon diluent higher boiling than the diacetylenically unsaturated hydrocarbons being distilled by at least 5C at the pressure of the distillation. Such inert hydrocarbons include the higher boiling paraffins, naphthenes and aromatics including partially hydrogenated aromatics. In general, these inert hydrocarbons have boiling points of above 200C at atmospheric pressure. The paraffinic hydrocarbons useful include both straight and branched chain while the naphthenic hydrocarbons include alkyl substituted naphthenes and polycyclic naphthenes. Aromatic hydrocarbons useful include the alkyl benzenes, alkyl naphthalenes, and the like, high boiling polycyclic condensed ring and noncondensed ring aromatics such as phenanthrene, anthracene, diphenyl, dimethyl diphenyl, and high boiling partially saturated aromatics such as tetralin, fluorene, acenaphthene, and the like. Particularly useful are the triethyl benzenes, tetramethyl benzenes, tetraethyl benzenes, tetralin, diphenyl, methyl diphenyl, methyl diethyl benzenes, naphthalene, methyl naphthalenes, and the like, as well as mixtures thereof. The choice of the particular inert diluent employed is most frequently based on such practical considerations as availability, costs, ease of handling, i.e., whether normally liquid or solid, and like. considerations. Additionally, it is preferable to take into consideration the apparent efficiency of the distillation apparatus since for a clean separation, the boiling temperature difference between the diacetylenically unsaturated compound and the inert diluent is greater as the distillation apparatus becomes less efficient. The primary considerations, in accordance with the present invention, are that the inert diluent must have a minimum boiling point at least 5C,

preferably 10C above the maximum boiling point of inert hydrocarbon diluents are the triand the tetratemperatures, pressures ranging below about 200 mm.

Hg, preferably below 20 mm Hg, are employed.

While the present distillation process is primarily directed toward the distillation of diacetylenically unsaturated compounds, it may be employed in the distillation of other high boiling readily polymerizable unsaturated compounds such as divinyl aromatics, monoacetylenically unsaturated hydrocarbons, and the like. However, the process of the present invention is most useful when employed in the distillation of the readily polymerizable diacetylenically unsaturated aromatic hydrocarbons such as diethynylbenzenes, ethynylpropynyl benzenes, and the like, as well as such hydrocarbons containing non-hydrocarbon substituents such as halogens, i.e., chlorine and bromine, amino groups,

EXAMPLE i To demonstrate the efficacy of the present invention a series of seven stability tests were carried out by heating diethynylbenzene for several hours at 200F nitio groups acid i hydroxygioups and the like' (93C). In one of the tests diethynylbenzene was In Its prefeqed apphcgnon h dlstluauoi p f of heated alone and in tests 2 through 5 various inhibitors the present invention is applied to the distillation of were added while in tests 6 and 7' heming was in mc dlethynylbenzenesi presence of an inert hydrocarbon diluent. The specific The i Ofmert hydrocarbon dlluem employe.d 0 composition of the material subjected to the above may vary wldely however the amount employed 1 conditions in each of the seven tests were as follows: most often represent a concentration of greater than TEST volume of the mixture resulting from its admixture 1 Diethynylbenzene with the diacetylenically unsaturated compounds being N0 2 Diethynylbenzene Containing 0.16 wt distilled. Preferably, however, the concentration of butyl Catechol (TBC) such inert hydrocarbon diluent in such mixture is 3 Diethynylbenzene Containing 0 1 wt TBC greater than 35 volume While above these limits, and 0.5 Wt. Sulfur virtually any amount of inert hydrocarbon diluent may N0 4 Diethynylbenzene containing 016 WL h be employed, seldom is it used in concentration of droquinone greater than 60 volume in its admixture with the 5 Diethynylbenzene containing 035 diacetylenically unsaturated compounds being disk tmed- No. 6 Diethynylbenzene in 1:1 admixture with tet- In carrying out the process of the present invention methyl benzene as a continuous operation, the feed containing NO 7 C i i f6 Containing 1 wt TB diacetylenically unsaturated compounds and the inert hydrocarbon diluent y be both Continuously intro" *Registered trademark of Naugatuck Chemical Dividuced in pre-admixture with one another or each may ign f U i d St t R bb C be continuously introduced separately into the distilla- Th character of the heated material was periodically tion apparatus. In the continuous distillation of the observed and recorded with reference to polymerizadiacetylenically unsaturated compounds, usually the tion. Table 1 following presents the results of the peridiacetylenic compounds are continuously taken overodic observations for the seven tests.

TABLE I Number of Hours Test Test Test Test Test Test Test at 200F No. 1 No. 2 N0. 3 No. 4 No. 5 No. 6 No. 7

24 dark dark dark dark sl dark clear clear 36 solid solid solid solid solid clear clear 60 darker darker 84 same same 108 same same I32 same same 136 polymerizing polymerizing head or as a side draw, if lighter materials are present, EXAMPLE II with the heavier materials and the inert hydrocarbon A series of foul. tests was carried out to demonstrate diluenhbeing continuously taken from the bottom of the effect of the concentration of inert hydrocarbon h qistlllation apparatus' If f Course the diluent in the diacetylenically unsaturated compound. Manon P of the prfesem Invention m y be f In each test, diethynylbenzene was the diacetylenically ried out batchwise or semi-continuously with intermit- 5O unsaturated Compound and triethylbenzene was the tent introduction of either the diacetylenically unsatut inert hydrocarbon diluem [n all tests the mixture was rated compound Containing feed or the inert hydrocar heated at 240F. Table II below describes the character b diluent of the diethynylbenzene after various time periods for The type of distillation equipment employed for the h f th f t t r process of the present invention may be any of that TABLE H conventionally employed and may range in efficiency q slmple fl dl.stl.nan.on apparatus to Very lgh ef N0 Hours Concentration of triethylbenzene in ficiency multitray distillation columns. As hereinabove heated at diethynylbenzene indicated, however, as the efficiency of the distillation 15% 34% 44% 53% apparatus goes down, it frequently is desirable to in- 2 dark OK OK OK crease the temperature spread between the diacetyleni- 4 dark sLdark OK OK cally unsaturated compounds being distilled and the g f z 2:3: 33:: inert hydrocarbon diluent being used. viscous To further describe and to specifically exemplify the Solid f S Same present invention, the following examples are pres- 14 v sco s Same ented. These examples are not to be construed as limiting the scope of the present invention, however.

EXAMPLE III To further demonstrate the present invention, two separate fractionations were carried out on 1,500 grams of the same 95% by weight diethynylbenzene fraction. In one fractionation, referred to as Run A, the diethynylbenzene fraction was added to the stillpot and the diethynylbenzene distilled therefrom. In the other fractionation, referred to as Run B, the diethynylbenzene fraction was diluted with an equal volume of tetraethylbenzenes and then the diethynylbenzene distilled overhead. In both Run A and Run B, the distillation was carried out at an overhead pressure of [-2 mm Hg and the overhead product was 99% by weight diethynylbenzene. In Run A the overhead temperature was 43-47C while in Run B, the overhead temperature was 47C. The maximum stillpot temperature in Run A was 100C and Run B was 110C. It was found that in Run A, a substantial amount of polymer coated the wall of the stillpot while in Run B, no polymer formed in the stillpot.

What is claimed is:

1. A process for the distillation of high boiling diacetylenically unsaturated aromatic hydrocarbons comprising subjecting to distillation conditions within a distillation zone a distillation mixture consisting essentially of said high boiling diacetylenically unsaturated aromatic hydrocarbon and a high boiling aromatic hydrocarbon diluent, said diluent having a minimum boiling point at least 5C. higher than the boiling point of said diacetylenically unsaturated aromatic hydrocarbons being distilled and being present in an amount greater than volume percent of the mixture resulting from its admixture with the diacetylenically unsaturated compounds being distilled, said distillation being carried out under vacuum sufficient to maintain a maximum distillation temperature below l5()C., and separating overhead pure diacetylenically unsaturated aromatic hydrocarbon whereby polymerization of said diacetylenically unsaturated aromatic hydrocarbon during distillation is substantially prevented.

2. The process of claim I wherein said diacetylenically unsaturated aromatic hydrocarbon is diethynyllenes, and mixtures thereof. 

1. A PROCESS FOR THE DISTILLATION OF HIGH BOILING DIACETYLENICALLY UNSATURATED AROMATIC HYDROCARBONS COMPRISING SUBJECTING TO DISTILLATION CONDITIONS WITHIN A DISTILLATION ZONE A DISTILLATION MIXTURE CONSISTING ESSENTIALLY OF SAID HIGH BOILING DIACETYLENICALLY UNSATURATED AROMATIC HYDROCARBON AND A HIGH BOILING AROMATIC HYDROCARBON DILUENT, SAID DILUENT HAVING A MINIMUM BOILING POINT AT LEAST 5*C. HIGHER THAN THE BOILING POINT OF SAID DIACETYLENICALLY UNSATURATED AROMATIC HYDROCARBONS BEING DISTILLED AND BEING PRESENT IN AN AMOUNT GREATER THAN 15 VOLUME PERCENT OF THE MIXTURE RESULTING FROM ITS ADMIXTURE WITH THE DIACETYLENICALLY UNSATURATED COMPOUNDS EING DISTILLED, SAID DISTILLATION BEING CARRIED OUT UNDER VACUMM SUFFICIENT TO MAINTAIN A MAXIMUM DISTILLATION TEMPERATURE BELOW 150*C., AND SEPARATING OVERHEAD PURE DIACETYLENICALLY UNSATURATED AROMATIC HYDROCARBON WHEREBY POLYMERIZATION OF SAID DIACETYLENICALLY UNSATURATED AROMATIC HYDROCARBON DURING DISTILLATION IS SUBSTANTIALLY PREVENTED.
 2. The process of claim 1 wherein said diacetylenically unsaturated aromatic hydrocarbon is diethynylbenzene.
 3. The process of claim 1 wherein said high boiling aromatic hydrocarbon is one selected from the group consisting of triethyl benzEnes, tetramethyl benzenes, tetraethylbenzenes, tetralin, diphenyl, methyl diphenyl, methyl diethyl benzenes, naphthalene, methyl naphthalenes, and mixtures thereof. 